1. Field of the Invention
This invention relates in general to submersible rotary well pumps rotated by rods from a motor located at the surface, particularly progressing cavity well pumps, and a means for preventing excessively high speed reverse rotation should the pump lock up.
2. Description of the Prior Art
A progressing cavity well pump assembly includes an electrical motor located at the surface. The electrical motor rotates an input shaft of a gear box. The gear box reduces the rotational speed on an output shaft. The output shaft is connected to a string of rods that extend to a rotor located in the well. The rotor is rotated inside a stationarily mounted stator.
In case the level of fluid in the well dropped too much, the added friction of the rotor rotating inside the stator would generate excessive heat. Eventually, the rotor can seize and lock up inside the stator. The string rods may be up to or more than 4,000 feet in length, consequently, the electrical motor will continue applying torque to the rods, twisting them, to a considerable degree before the motor finally reaches its limit and stops rotating. Then, the energy stored in the rods due to the torque imposed will cause the rods to begin to unwind, rotating the motor in reverse. The high amount of energy can cause the speed to be so high so as to damage the drive components at the surface.